Iodine is a black-blue-to-violet crystalline solid at standard temperatures and pressures and is only sparingly soluble in water at 20.degree. C. (0.29 g/100 g). Traditionally, crystalline iodine is dissolved in water by the addition of small amounts of KI, which greatly enhances the dissolution of the iodine. Dissolved I.sub.2 hydrolyzes to form HOI in amounts proportional to the pH of the solution, wherein above pH 8.5, iodine is present almost exclusively as HOI (Chang, 1958). Both dissolved I.sub.2 and HOI possess antipathogenic properties. At low pHs, e.g., 5-7, iodine exhibits antibacterial action, whereas at higher pHs, e.g., 8-10, it is an efficient virucide. Chang (1958) reports that above pH 8, HOI decomposes slowly to form iodide and iodate ions, especially in the presence of dissolved iodides; neither iodides nor iodates have found to be germicidal to date. Further, I.sup.- may react with I.sub.2 to form the highly coloured I.sub.3.sup.- ion, which is also ineffectual as a germicide. Based on elementary thermodynamic principles, the addition of dissolved iodine to water will significantly reduce the freezing point of the water to which it is added.
The disinfectant properties of iodine have been known since the 19.sup.th century and, indeed, iodine was employed on a large scale for water disinfection during World War I.
The use of iodine as a food additive has been limited mainly to the addition of KI to NaCl (table salt) to produce so-called "iodized salt", which is used as the primary source of consumed iodine in North America. The beneficial biochemical effects of iodine have been well documented since about the turn of the century. In emergency situations, up to 10 ppm iodine may be consumed for short periods of time according to USEPA guidelines on drinking water quality, without being considered toxic to humans. Iodine has been added to food products per se only to prevent diseases associated with iodine deficiency, e.g., goitre and mental retardation. As a result, iodine as a food disinfectant germicidal inhibitor or as a preservative, in the context of preventing decay of food by micro-organisms has not been reported.
Although iodine is readily added to liquid water which can be subsequently frozen, almost no systematic work has been published concerning the behaviour of iodinated water-ice. There are no easily available tables, for example, documenting the lowering of the freezing point of water with increasing concentrations of dissolved iodine, in whichever chemical form. Further, no work has been published concerning the biocidal/biostatic nature of iodinated water-ice.
Ice and water-ice mixtures have been used as a refrigerant for several millenia and their use as an industrial refrigerant is also still prevalent today, especially with the need to deliver unspoiled, perishable foodstuffs to market in mass quantities by meat and produce suppliers across the world. Although the cooling of foodstuffs to near or below freezing temperatures, i.e. at or below 0.degree. C. does prevent their spoilage in large measure, it does not always ensure that any potential airborne, iceborne or waterbome pathogens with which the foodstuffs may have come into contact are rendered harmless to human consumers. That is, although ice may preserve foodstuffs from heat spoilage and chemical breakdown, it does not possess antibiotic qualities. Ice is just as able to preserve bacteria, viruses and cysts within the ice itself or on the surfaces of foodstuffs as it is able to somewhat preserve and protect the foodstuffs themselves.
Chilled or refrigerated fish quality declines rapidly, due in large measure to the presence of spoilage bacteria (Liston, 1982). The number of these spoilage bacteria present, therefore, has a profound effect on the shelf life of these fish. With fish being stored in the holds of trawlers for sometimes many days before landing, any effective bacterial inhibitor will have a significant impact on the quality of the fish when it reaches the processing plant. This is of prime importance today when stocks of some species, such as cod are low, but demand remains high.
It should be recognized that several problems exist in using ice as both a refrigerant and preservative of foodstuffs. The main problem is that many common pathogens are well able to survive cooling to 0.degree. C. and below. Cooling to these temperatures only serves to prevent breakdown and spoilage of the foodstuff due to heat, and may slow, but not eliminate pathogenic activity. In fact, some pathogens, especially viruses, are quite able to flourish at freezing temperatures. For example, fish infected by a pathogen and subsequently stored on ice may emerge from storage being more heavily laden with pathogen than before it was stored. In this case, not only does the fish emerge infected, but so does the ice-melt-water used to store the very fish it was meant to protect. "Spent" or used ice or melt-water would then become a viable biohazard and the storage vessels themselves would become contaminated and become vectors for future infection of foodstuffs.
There, thus, remains a need for a biologically safe refrigerant system involving ice whenever alternative mass storage and delivery of vulnerable foodstuffs systems are not available. The need is particularly significant where the foodstuff intrinsically contains bacteria, e.g. fish products, and spoilage caused by the growth of such bacteria must be avoided.